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Old 10-06-2008, 10:12 PM   #1 (permalink)
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Low RPM power from EV motors possible?

I've been thinking about a project to add some E-motor power to the
rear-end of my formerly 4WD CRV. A mild hybrid?
With the rear differential deleted, those rear wheels are just sitting back there free-wheeling.. Doing nothing.

So, I've been wondering if there is any off-the-rack motor/controller that could be connected directly to a rear axial shaft to add a few HP of EV power to my old CRV?

This would be an ICE assist system and wouldn't need to run in total EV mode.
My goal would be to add 5 to 10 HP of power to the rear wheels while the car was at highway speeds, & have regen if possible..


From what I've seen of EV motor specs, low rpm (wheel speed) with good HP isn't possible.

Looking for some advice please..

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Old 10-06-2008, 11:30 PM   #2 (permalink)
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Add some gearing to get the electric motor up to a decent speed compared to the rotation of the wheels?
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Old 10-06-2008, 11:32 PM   #3 (permalink)
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I believe your idea has much merit, Xringer.

I always thought that electric motors excelled at producing gobs of torque at low RPMs, allowing Forkenswift and the ElectroMetro to operate using only a couple of gears and no clutch.

But I've never built an EV.
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Old 10-07-2008, 12:01 AM   #4 (permalink)
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What kind of motor speed do you need?
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Old 10-07-2008, 12:30 AM   #5 (permalink)
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Quote:
Originally Posted by Ryland View Post
What kind of motor speed do you need?
Well I'm not 100% sure.. I think my tires are about 7' around and do 754 revs per mile.
So, a mile-a-minute would be 754 RPM on the end of that little shaft.

or, maybe even both shafts.
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Old 10-07-2008, 03:01 PM   #6 (permalink)
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If you plan on driving both back wheels, you'll still need a differential back there, won't you? What happened to your rear diff?
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Old 10-07-2008, 03:39 PM   #7 (permalink)
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Quote:
Originally Posted by Joe_Bloe View Post
If you plan on driving both back wheels, you'll still need a differential back there, won't you? What happened to your rear diff?

I was thinking about that.. I've got a few ideas.
1. Drive one wheel. (Go around in circles?)

2. Install two motors, one for each wheel. (Small pancake motors, or shorten the shafts).

3. Reinstall the rear diff and good sized motor to drive it.

But that's going to take some extra HP to over-come Honda's fancy dual-pump clutch activator gizmo. Bigger motor etc.
The motor would connect to those 4 bolt holes in the upper left.


One crazy idea was to attach a motor to the transfer case output from the front end and drive the front wheels..
That's also a low RPM app.

video:
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Old 10-07-2008, 11:00 PM   #8 (permalink)
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Quote:
Originally Posted by Tango Charlie View Post
I believe your idea has much merit, Xringer.

I always thought that electric motors excelled at producing gobs of torque at low RPMs, allowing Forkenswift and the ElectroMetro to operate using only a couple of gears and no clutch.

But I've never built an EV.
I've never built one either, but about 10 years ago, I watched a co-worker put his EV together. I learned that building an EV is not an easy task. Something I would rather not try myself.

But, if I could convert my CRV into a mild hybrid for a reasonable cost, in time and money, that seems like a worthwhile goal.

I was just reading about the controller and other hardware used by Netgain
to convert ICE cars and trucks. http://www.go-ev.com/
And it seems pretty complicated at first glance.

Maybe I should start off with EV go-cart.?.
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Old 10-08-2008, 10:04 AM   #9 (permalink)
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if your diff is OK, what about this:

mate up a cheap CVT from a scooter to the input of the diff. put the 5-10kw motor on the CVT. That way you get some torque multiplication at low speeds, but at high speeds when you want the motor to free-wheel, the CVT will gear the motor higher and reduce drag.
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Old 10-08-2008, 12:25 PM   #10 (permalink)
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Quote:
Originally Posted by Joe_Bloe View Post
if your diff is OK, what about this:

mate up a cheap CVT from a scooter to the input of the diff. put the 5-10kw motor on the CVT. That way you get some torque multiplication at low speeds, but at high speeds when you want the motor to free-wheel, the CVT will gear the motor higher and reduce drag.
I'm not sure a CVT or anything would be needed.
The Honda RT4WD system works kinda different. When the rear wheels turn,
they drive a pump(s?) and so does the propeller shaft from the transfer case up front. (The call it a Dual-Pump system).

If the front wheels start turning faster than the rears rear wheels,
(ice or mud) the difference in pump pressure engages the clutch,
allowing drive to the rear wheels..

So, all I would need to do to engage the rear wheels, is put some good
RPMs on the diff.. (Trick it into thinking the front wheels were spinning)..

I would rather not mess with that thing, since it's going to load up the wheels and it's heavy..

It would be a lot easier just to drive one wheel..
What would be the drawbacks to that?

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